1. Field of the Invention
This invention relates to electronic engine controls for an internal combustion engine.
2. Prior Art
It is known to control the air fuel ratio of an internal combustion engine using various air fuel control strategies. Many factors, such as ambient air pressure, manifold absolute pressure, intake air temperature, have been used in the process of controlling air fuel ratio for an internal combustion engine.
Further, the proper operation of a catalyst processing the exhaust gas from an internal combustion engine depends, in part, upon the air fuel ratio supplied to the engine. Thus, the operational characteristics of the catalyst may be important in determining the proper air fuel ratio. Also, it is known to use an exhaust gas oxygen sensor to sense the concentration of oxygen in the exhaust gas. Knowledge of the exhaust gas oxygen concentration can be used to control the air fuel ratio. It would be desirable to improve control of the air fuel ratio and operation of an exhaust gas oxygen sensor.
It is known to provide heaters for exhaust gas oxygen sensors. However, it has been difficult to control such heaters to become activated only when they are needed because control has typically been time dependent. Other previous approaches have used exhaust gas temperature prediction strategy to estimate the catalyst midbed temperature and the exhaust gas temperature measured near the exhaust flange. If heat is applied too soon to such exhaust gas oxygen sensors, the sensors may crack in the presence of moisture in the exhaust gas. Further, if too much heat is applied to the exhaust gas oxygen sensor, the sensor may not function properly. It would be desirable to improve operation of the exhaust gas oxygen sensor and associated heaters.